The invention relates to an electromechanical adjusting device for the carrier frame of beds having a pivotable foot and/or head part on which actuating arms act, said arms being fixed to an adjustable shaft which is mounted crosswise to the plate carrier and which may be, for example, constructed as a square tube, the adjustable shaft carrying the adjusting device containing an electric motor arranged with its rotor shaft at right angles to the adjustable shaft in an insulating protective casing and supported at the other end on the carrier frame. Such devices are known from German Offenlegungsschrift No. 2,326,709 and British Patent Specification No. 1,044,500 in which linear servomotors are shown, the drive rod of which moves the adjustable shaft via a lever fixed thereto. This conversion of the linear motion into the rotary motion of the adjustable shaft with the aid of levers is also known from earlier hydraulic adjustable drives which may be seen for example, in British Patent Specification No. 855,112, but these are not suitable because of their fairly high susceptibiblity to faults.
When using drive levers acting on the adjustable shaft, it may be noted that, in a disadvantageous manner, the different angular positioning of the lever results in a different rotary moments to be exercised on the adjustable shaft. As a result of this, the power of the adjustable drive must always be matched to the most unfavourable conditions and this leads to a certain amount of overdimensioning of the drive. Furthermore, the levers as well as the remaining components becoming necessary represent additional outlay and makes assembly work more difficult and more expensive.